Combustor

ABSTRACT

A casing for a combustor of a gas turbine engine has a plurality of apertures, each aperture being reinforced with a band of material dividing the aperture. The casing and reinforcing member are forged simultaneously with the reinforcing member aligned with the direction of maximum stress field.

This invention relates to a casing. More particularly this inventionrelates to a casing for a combustion chamber of a gas turbine engine.

A ducted fan gas turbine engine generally comprises, in axial flowseries, an air intake, a propulsive fan, an intermediate pressurecompressor, a high pressure compressor, combustion equipment, a highpressure turbine, an intermediate pressure turbine, a low pressureturbine and an exhaust nozzle.

The structure and operation of all these components is generally wellknown and consequently, with the exception of the combustion equipment,will not be described in great detail in this specification.

Combustors and combustor casings can have a large number of apertures.The apertures allow access for components such as fuel manifolds, probesand ignitors which, partly due to the high temperatures within thecombustion chamber, must necessarily by positioned externally of thecombustion chamber outer casing.

The apertures must be reinforced against stresses. Traditionally this isachieved by reinforcing the rim of the aperture with some of thematerial from which the casing is formed.

The casing and rim reinforcement are typically formed by casting orforging. In a forging process a volume of material is heated shaped bytwo or more dies. The material undergoes plastic deformation andconforms to the shape of the die. The volume of the material does notalter significantly in the forging process.

Where provision for apertures are formed as part of the forging processa volume of material equal to the size of the aperture must formed. Insome areas this volume of material may be used to form the reinforcingrims of the apertures, in other areas the volume of material isdispersed around the casing and must subsequently be removed.

Where the aperture requires reinforcement greater than the casingthickness an additional volume of material must be added in the forgingprocess.

Gas turbines have weight and cost considerations that must be addressed.Where a turbine provides thrust for a transport device such as a ship orplane reducing the weight of the engine can have a beneficial effect onthe efficiency of the transport device and can lead to a reduction inthe fuel consumption.

It is an object of the present invention to seek to provide an improvedreinforced aperture.

According to the present invention there is provided a combustion casingfor use in a gas turbine, the casing having an aperture extendingtherethrough, characterised in that the aperture has a reinforcingmember extending across and dividing the aperture.

Preferably the aperture has a rim extending around the periphery of theaperture and preferably the rim is raised from a substantially planararea of the casing.

Preferably the reinforcing member is integral with the rim.

Preferably the rim and the reinforcing member are formed simultaneouslyby casting, sintering or forging.

Preferably the rim is integral with the casing.

Preferably the rim and the casing are formed simultaneously by casting,sintering or forging.

The rim may be subject to a stress field and preferably the reinforcingmember is orientated so as to align with the direction of maximum stressfield. The reinforcing member may be a single or plural bar that may bestraight, curved or serpentine.

The term “casing” in this specification includes hoods, cowling, sheets,combustors, combustor casings and other components having similarfunctionality to the above.

The present invention will now be described, by way of example only,with reference to the accompanying drawings in which:

FIG. 1 depicts an annular combustion chamber

FIG. 2 is a conventional aperture in the combustion chamber casing

FIG. 3 is an aperture according to the present invention.

FIG. 4 depicts a gas turbine engine having a combustor with a casing inaccordance with the present invention.

FIG. 1 depicts annular combustion equipment for a gas turbine engine.The combustion equipment consists of an annular combustion inner casing20, and a coaxial annular combustion outer casing 22. The combustionchamber 24 is coaxial with and positioned between the inner casing 20and the outer casing 22.

The combustion chamber 24 is defined by an outer combustor wall 26 andan inner combustor wall 28, the internal volume being adapted to allowmultiple combustion zones.

A series of regularly spaced fuel injectors 30 extend through a bulkhead32 that forms one wall of the combustion chamber. The fuel injectors mixair with fuel and eject it into the combustion chamber as a finelydispersed mixture.

Fuel is supplied to the injectors via a conduit that extends throughapertures in the combustion outer casing 22. Also extending throughapertures in the combustion chamber outer casing are igniters thatignite the finely dispersed air and fuel mixture injected into thecombustion chamber by the fuel injectors.

FIG. 2 depicts an aperture 40 in the combustion outer casing that hasbeen formed by a forging process. The aperture has a rim 42 that israised from the local surface of the combustion outer casing 22. Aflange 44 is provided on the combustion outer casing for connection witha high pressure compressor housing.

The material of the combustion outer casing is a high temperature nickelalloy or steel. The rim reinforces the casing against stresses that arecreated by the presence of the apertures and movement induced bypressure fluctuations in the combustor.

To adequately overcome hoop stresses the volume of material within therim is typically equal to that lost in the formation of the aperture.

FIG. 3 depicts a reinforcing member for an aperture according to thepresent invention. The reinforcing member 50 extends across the apertureand is formed during the forging process. The member is aligned to alignwith the direction of maximum stress field. The stress fields may bedetermined either empirically or by routine calculation.

A reinforcing member of this type uses significantly less volume ofmaterial than that of the prior art to achieve an equal or betterreinforcement. The overall volume of material for the casing is reduced.Where a large number of apertures are provided, as in the combustorouter casing, it can result in lower forging and machining costs and asignificant cost saving in the amount of material required as well as areduction in the weight of the component.

Where reinforcement is achieved through the provision of a reinforcementmember of the present invention it is possible to increase the size ofthe aperture without loss of functionality due to detrimental effectscaused by stresses on the component. The cost and weight savings offeredby the present invention are thereby further enhanced.

FIG. 4 is a schematic of a gas turbine engine incorporating a combustorwith a casing of the invention. The gas turbine engine has a fan 102, anintermediate compressor 104, a high pressure compressor 106, an annularcombustor 108, a high pressure turbine 110, an intermediate pressureturbine 112 and a low pressure turbine 114

It will be appreciated that other embodiments may be apparent to theskilled reader without departing from the inventive concept of thepresent invention.

Each feature described herein may be incorporated into the claims eitherindependently or in combination with any other feature.

1. A combustion casing for use in a gas turbine, the casing having anaperture extending therethrough, wherein the aperture has a reinforcingmember extending across and dividing the aperture.
 2. A casing accordingto claim 1, wherein the casing is annular.
 3. A casing according toclaim 1, wherein the aperture has a rim extending around its periphery.4. A casing according to claim 2, wherein the rim is raised from asubstantially planar area of the casing.
 5. A casing according to claim2, wherein the reinforcing member is integral with the rim.
 6. A casingaccording to claim 2, wherein the rim and the reinforcing member areformed simultaneously by casting, sintering or forging.
 7. A casingaccording to claim 2, wherein the rim is integral with the casing.
 8. Acasing according to claim 2, wherein the rim and the casing are formedsimultaneously by casting, sintering or forging.
 9. A casing accordingto claim 2, wherein the rim is subject to a stress field, thereinforcing member being orientated so as to align with the direction ofmaximum stress field.
 10. A gas turbine engine incorporating a combustorcasing as claimed in claim 1.